The present invention relates in general to sheet feeding equipment and in particular to a new and useful sheet separator for sheet feeders, which includes a mechanism for regulating and adjusting the passage gap between a retaining member for holding back sheets in the stack, and a friction cylinder which is rotatable for feeding one sheet from the stack.
Such sheet feeders are known per se. There are sheet feeders having their retaining member rigidly fixed in its adjusted position, thus defining a passage gap which cannot be changed up to the next adjustment (German patent No. 1,261,132). In other sheet feeders (German OS No. 25 38 957), the radial spacing however, after an adjustment, the member is displaceable against a spring actin so as to enlarge the passage gap. While designs with fixed retaining members start from the assumption that the paper sheet thickness within a single stack is constant, within usual tolerances, designs with a resiliently mounted retaining member provide a possibility of handling sheets of varying thicknesses within a single stack, with the requirement, however, of initially adjusting the minimum sheet thickness.
In neither of these kinds of feeders, however, can the paper passage gap be adjusted exactly with certainty, since no proper measuring and indicating equipment is provided. In prior art feeders, while adjusting the passage gap to a certain paper thickness, initially, the sheet is inserted into a larger gap and with the friction cylinder at a standstill. Then, the gap is narrowed by correspondingly readjusting the retaining member, until, with the friction cylinder remaining at a standstill, the sheet can be moved between this cylinder and the retaining member only under considerable frictional resistance. The adjustment thus depends on the feeling of the adjuster, and it is particularly critical, i.e. uncertain, with thin paper, since there is no absolute measure of accuracy in this regard.